1. Field of the Invention
This invention relates to catalysts useful for the homopolymerization or copolymerization of .alpha.-olefins of 2-12 carbon atoms.
2. Prior Art
A variety of catalysts have been proposed for use in the production of polyolefins, typical examples of such catalysts being those having transition metal compounds such as titanium or vanadium supported on solid compounds such as magnesium halide, magnesium oxide, magnesium hydroxide and other inorganic magnesium compounds. These conventional catalysts had a drawback in that the polymer produced therewith is relatively small in both bulk density and average particle size and predominant in objectionably minute granules. Such prior catalysts were further responsible for the development of dusts during the molding of the polymer and hence for reduced efficiency of polymer processing.
There are known certain other types of catalysts are disclosed for example in Japanese Patent Publication No. 43-2211, Japanese Laid-Open Patent Publication Nos. 54-148093, 56-47407 and 58-21405, which catalysts comprise titanium or vanadium and/or inorganic magnesium solids supported on particulate carriers of SiO.sub.2 or Al.sub.2 O.sub.3. These catalysts are reportedly capable of providing polymers with increased bulk density and greater average particle size, but need further improvement before such polymers can be readily put into molding or other processing apparatus without being first pelletized.